Contents of the LANWRDS1.TXT file

This glossary was taken from LAN magazine (March 1991 and April 1991).It covers terms from A - M.

802.3: The numerical designation for the International Electrical andElectronics Engineers (IEEE) standard governing the use of the CarrierSense Multiple Access with Collision Detection (CSMA/CD) media-access method.Although CSMA/CD and Ethernet are used interchangeably, there aretechnical differences.

802.4: The numerical designation for the IEEE standard governing the useof the token-passing, bus-based, media-access method. In token-passingnetworks, an electrical signal, or token, is passed from one stationto another. Only when a station has possession of the token can ittransmit data.

802.5: The designation for the IEEE standard governing the use ofthe token-passing, ring-based, media-access method. Token Ringnetworks are wired electronically, or logically, in a closed circle,or ring. Physically, however, Token Ring networks are wiredin a star configuration, with a centralized wiring hub providingthe electrical circuits that form the logical ring.

1OBase1: The implementation of the 802.3 standard known asStarlan. Starlan runs on baseband media at 1 million bits (or 1 Megabit)per second (IMbps). Starlan limits cable segments to 500 meters.

1OBase2: The implementation of the 802.3 standard also known as thinnet.1OBase2 networks operate over thin coaxial cable, at 10Mbps.The 1OBase2 standard limits cable segments to 200 meters. Thin coax getsits name because its diameter is about half that of "standard" Ethernet.

Advanced Program-to-Program Communications (APPC): An IBM protocol forcommunication between PCs in a mainframe-based network; APPC ensures thatprograms have access to network resources when they need them and thatnetwork resources are not corrupted.

American National Standards Institute (ANSI): The principal standards settingbody in the U.S.; ANSI represents the U.S. in the International StandardsOrganization (ISO).

Analog transmission: A transmission method that continually varies awaveform over an infinite range of voltage.

AppleTalk Filing Protocol (AFP): The set of services within Apple Computer'sAppleTalk network protocol that handles remote file access across a LAN.AFP is a presentation-layer service within the sevenlayer Open SystemInterconnection (OSI) reference model.

AppleTalk Link Access Protocol (ALAP): The set of services that governspacket transmission across an AppleTalk network. ALAP operates at theOSI data-link layer.

Asynchronous transmission: A data exchange format controlled by startand stop bits at the end of each character. It is also characterizedby the lack of predetermined time intervals between the transmissionof characters. Contrast with synchronous transmission.

Attachment Unit Interface (AUI): The connector used with thick Ethernetthat often includes a cable (called a drop cable) running off the main,or backbone, coaxial cable.

Back-end processes: The functions performed by a database server inresponse to directions from an application running on an end-user PC.

Bandwidth: The data-carrying capacity of a transmission medium, usuallymeasured in Hertz, which equals cycles per second.

Baseband: A data-transmission technique that uses the entire bandwidthof a media, without modulating a digital signal. Ethernet, Token Ring,and Arcnet use baseband transmission. Contrast with broadband.

Bindery: The term used for the database of names, passwords, groups,and accounting for Novell's NetWare network operating system.

Bridge: A networking device that connects local or wide area networksusing the same data-link layer protocol. Bridges operate at the datalink layer in the OSI reference model. Contrast with router.

Broadband: A data-transmission technique that allows multiple signalsto share the bandwidth of a transmission media. Cable TV is a broadbandtransmission in that signals for multiple TV stations are carried overseparate channels. Contrast with baseband transmission.

Broadcast: A message that is sent to all nodes in a network.

Brouter: A networking device that combines some of the capabilities of abridge with those of a router-that is, it routes specific protocolswhile bridging others.

Bus topology: A network architecture in which all the nodes areconnected to a single cable, which is terminated at each end.

Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA): Thenetwork-access method used by LocalTalk networks. With CSMA/CA, networknodes send out a "request to transmit" signal that alerts the otherstations on the network that it plans to send data. When the nodereceives a "clear to send" signal from the receiving node, it beginsto transmit.

Carrier-Sense Multiple Access with Collision Detection (CSMA/CD): Thenetwork-access method used by Ethernet networks. In CSMA/CD, all thenodes on a network contend equally for access to the transmissionmedium. If two nodes attempt to send data at the same time, they"sense" each other's signal and abort their transmission. Theyboth retry after waiting a random period of microseconds.

Consultative Committee for International Telegraphy and Telephony (CCITT):The standards-setting body that defines international data-communicationsstandards.

Client: A personal computer that requires services over a networkfrom a server.

Coaxial cable: A multilayered data transmission media with a single-wireconductor at its center surrounded by several insulating materials.These insulators include metal and rubber or plastic shields that protectthe conductor from electrical noise.

Database server: A computer that stores data centrally for networkusers; often uses client-server software to distribute the processing ofthat data among itself and other workstations on the network.

Data Encryption Standard (DES): The U.S. government standard forscrambling and adding security codes (called keys) to data so it cannotbe deciphered by unauthorized network users.

Data-Link Control (DLC): Protocols governing packet information; theseinclude destination and source addresses and different control information.

Data-link Layer: Layer 2 of the OSI reference model; it defines protocolsgoverning data packetization and transmission to and from a node.

Direct-Memory Access (DMA): A process that grants peripherals access to acomputer's memory (i.e., random-access memory) independently of the centralprocessing unit (CPU). In most applications, including network 1/0, thisimproves system performance because it does not interrupt the CPU each timedata is moved in memory. Duplexing: The process of operating identical diskdrives or servers to maintain a fault-tolerant network environment. When thePrimary" system fails, the secondary system automatically takes over, thusensuring continued and uninterrupted network operation.

Electromagnetic/Radio Frequency Interference (EMI/RFI): Unwanted noise"created by current-producing devices such as electric motors and fluorescentlights. EMI/RFI affects the quality of the signal passing through datatransmission medium.

Electronic mail (e-mail): A network-based messaging system that exchanges"mail" electronically.

Enterprisewide network: The term used to describe a large organization'sinternetwork structure, including workgroups, departments, and offices.

Expanded Industry Standard Architecture EISA): A set of personal computer busstandards that extend the capabilities of the ISA bus developed by IBM forits original PC. EISA is compatible with ISA peripheral boards.

Fiber-optic cable: A data-transmission medium made up of a central glass (orplastic) fiber surrounded by a glass cladding and a plastic outer sheath.Fiber-optic cable transfers data by carrying modulated light from a laser orLED.

File locking: A data-management technique that reserves a file for the firstuser requesting it, locking out access to others in the process.

File server: A centrally located computer that acts as a storehouse of dataand applications for numerous users of a local area network. Most of thefile servers in use are adapted PCs. Newer servers were designedspecifically for file-server purposes.

Front-end: An application running on an end-user, or client, PC forpresenting, entering, and updating data.

Gateway: A device connecting two or more dissimilar networks or a networkwith a mainframe. Gateways operate at the session, presentation, andapplication layers. Contrast with bridge and router.

Government OSI Profile (GOSIP): The U.S. government-designed version of theOpen Systems Interconnection (OSI) reference model protocols.

Heterogenous network: A local or wide area network comprising hardware andsoftware from different vendors, usually implementing multiple protocols,operating systems, and applications.

High-Level Language Applications Programming Interface (HLLAPI): A set oftools developed by IBM to help programmers write applications to IBM'SSystems Network Architecture (SNA).

Hub: A wiring concentrator or repeater that brings together the connectionsfrom multiple network nodes. Although the true physical configuration of ahub-based network-called the network's topology-seldom fits the descriptionexactly, such networks are described as being "star wired."

Impedance: A measurement of the resistance to an electrical current that atransmission medium, such as coaxial cable, offers. Measured in ohms.

Industry Standard Architecture ISA): The peripheral-expansion architecture(called a "bus") developed by IBM for its PC, XT, and AT computers. Contrastwith EISA.

Institute of Electrical and Electronics Engineers IEEE): A professionalorganization that formulates computer and communications standards in theU.S. The IEEE works with a variety of other standards-setting bodies,including the International Standards Organization (ISO), in this process.

Integrated Services Digital Network (ISDN): A set of protocols proposed tocarry voice, data, facsimile, and video signals over a network.

International Standards Organization (ISO): A multinational standards-settingorganization that formulates computer and communications standards. The ISOis perhaps best known for its Open Systems Interconnection

Internet: A nationwide association of interconnected networks, mostly at U.S.colleges and universities; among organizations on the Internet are theNational Science Foundation and the Advanced Projects Research Agency. TheInternet is governed by the Internet Activities Board. The word internet(note the lower-case "i") is also used generically to describe any network ofLANs connected via bridges, routers, and/or gateways.

Internet Protocol (IP): The protocol that governs packet forwarding withinthe Transmission Control Protocol/ Internet Protocol suite of standardsdeveloped and used on the Internet.

Jabber: The term used to describe an error caused when a network interfacecard continually places corrupted data on the network.

LAN-aware applications: Software applications that implement record and filelocking over a network. Record and file locking, as their names imply, put a"lock" on a record (a specific piece of data) or file when an individualaccesses it; this prohibits others from accessing (and possibly corrupting)the data.

LAN-ignorant applications: Single-user applications, which generally are notrecommended for use on a LAN.

LAN Manager: The OS/2-based network operating system co-developed byMicrosoft and 3Com. A variety of other manufacturers, including AT&T andNCR, market vendorspecific versions of LAN Manager for their own hardwareplatforms.

Mirroring: A data-protection method in which a backup storage devicemaintains data identical to that on the primary device; the backup device canthus replace the primary device when it fails.

Modulation: The alteration of a signal's frequency, phase, or amplitude.

Mount: The method used by nodes on Network File Systems (NFS) and othernetworks to access network resources.

Multistation Access Unit MAU): A concentrator or transceiver for attachingnetwork nodes to a transmission medium.

Multitasking: The process of switching from one task to another withoutlosing track of either task. Usually accomplished by time-slicing of sharedresources-that is, dividing resource use into multiple segments, each ofwhich is assigned to a different task.